I was invited recently by a colleague to evaluate an older mare whose owner reported episodes of collapse while the mare was resting in her stable. These episodes had been increasing in severity over the previous year.

Occasionally the episodes happened while the mare was tied up outside her stable being groomed or while her owner was standing having a chat with another rider. Although the mare was only used for light hacking, her owner was very attached to her and understandably concerned at what was causing the episodes. In the absence of any clinical evidence of other causes of intermittent weakness or collapse such as heart disease or seizures, my colleague had made a presumptive diagnosis of “equine narcolepsy”. I admitted the mare to the clinic and set up a video camera overnight just outside her stable to capture the episodes.